Gov. Mitt Romney signed into law Wednesday a landmark health care bill designed to insure nearly all Massachusetts residents and set a national standard for other states to follow.

Even as he signed the bill, surrounded by state and congressional leaders at a ceremony steeped in fanfare at Boston's historic Faneuil Hall, Romney faced criticism for his decision to veto a key portion of the bill requiring all businesses that do not provide health insurance to pay a $295 annual fee.

The law, intended to require coverage for nearly all of Massachusetts' estimated 550,000 uninsured, has thrust the state to the forefront of the national debate about how to provide near-universal health care coverage without creating a single government-controlled system.

It's also a political coup for Romney as he weighs a potential run for the Republican presidential nomination in 2008. The law could be a centerpiece of that campaign if Romney can credibly claim pushing through a groundbreaking health care reform package.

Romney called the legislation a big step forward in health care reform.

"The reason this is so landmark is that we have found a way, collectively, to get all of our citizens insurance without some new government-mandated takeover or a huge new tax program," he said. "Instead the money we're spending on uncompensated care is going to be able to help people get insured and get the subsidy they need to buy that insurance they can afford."

The many speakers at the ticket-only event attended by more than 300 people were quick to congratulate each other on the bipartisan effort. Romney, a Republican mulling a 2008 presidential run, and Democratic U.S. Sen. Edward Kennedy shared the same Faneuil Hall stage for the first time since Romney's failed effort to unseat him in 1994.

"With the signing of this landmark health reform bill, after so many years of false starts, our actions have finally matched our words and we have lived up to our ideals," Kennedy said. "You have given Massachusetts just what the doctor ordered."

In addition to the $295 per-employee fee, the law provides subsidies and sliding-scale premiums to get poor and low-income residents into health plans. Those deemed able to afford insurance but who still refuse would face increasing tax penalties.

An ABC News-Washington Post poll of more than 1,000 adults nationwide released Wednesday found 55 percent of Americans would support a health care law similar to the Massachusetts model in their own states, with 41 percent opposed. The poll had a margin of error of plus or minus 3 percentage points.

Romney used his line-item veto power to strike eight portions of the bill, most significant the $295 fee. Administration officials say the fee could actually discourage registration for the new health program, since some employers might consider it cheaper to pay the fee than insure workers. Romney, in his veto, said it was not necessary to implement or finance the reform.

Leaders of the heavily Democratic House and Senate have said they would override any changes proposed by the governor.

House Speaker Salvatore DiMasi called the vetoes disingenuous, saying the law was crafted with concessions and compromise.

"To change anything will disturb the delicate balance that made this law possible," DiMasi said. "Each and every element of this law is critical to accomplishing our intentions and goals."

DiMasi said he wasn't sure if the governor was issuing the vetoes "for purposes of making the bill work or making him look good politically."

Business and hospital leaders also criticized the veto of the fee.

Massachusetts Hospital Association President Ron Hollander said the veto threatened the balance of the bill.

"I think it is important that all the parts and all the parties stay together," he said. "The employer assessment is critical."

Michael Widmer, president of the business-backed Massachusetts Taxpayers Foundation called the $295 assessment "a fair compromise that reflected the fact that one group of employers were subsidizing the free care costs of another group."

Romney, speaking to reporters after the event, defended his actions.

"There are many businesses who have been flooding my office with calls as well as business associations, that are very concerned about it," he said. "I made it very clear to both the House and Senate that I didn't believe the $295 made sense."

The Rev. Hurmon Hamilton of the Roxbury Presbyterian Church said there are still big questions left unanswered, especially just how affordable the low-cost plans called for in the bill actually will be. He said the one sour note in the hoopla-drenched event was the lack of poor people invited to the historic hall for the signing.

"What was missing from the picture was poor people and people of color, the diversity of the folks who ultimately will be affected and impacted significantly by the bill," he said.

Besides the $295 per-employee fee, the law provides subsidies and sliding-scale premiums to get poor and low-income residents into health plans. Those deemed able to afford insurance but who still refuse would face increasing tax penalties.

The plan is already drawing criticism from some who say the requirement that everyone have insurance, known as an "individual mandate," is an unacceptable expansion of government power. Some small business owners have also blasted the $295 fee, saying it could force them to fire workers or make it harder for them to expand.

The legislation also fails to flesh out some of the grittier details of the plan, including just how inexpensive the new low-cost health plans envisioned by the legislation will actually be.